The proposed work will be a continuation of the investigation of 5-substituted derivatives of the morphine alkaloids. 5-Methylhydrocodone, 5-methyldihydromorphone, 5-methylcodeine and 5-methylmorphine have already been prepared; 5-methylnaloxone and 5-methylnaltrexone are under preparation now. The preparation of 5-alkyl derivatives of etorphine and diprenorphine will be attempted, as will the conjugation of 5-carboxythebaine derivative with amino acids. All of these new substances will be submitted for pharmacological evaluation.